The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2001-61790, filed on Mar. 6, 2001, the contents of which is herein expressly incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a method and apparatus for attaching a pouch-shaped separator to an electrode plate of a battery.
2. Description of Related Art
A prismatic battery is constituted by placing an electrode plate group and an electrolyte in a battery case. The electrode plate group is composed of a plurality of square negative and positive electrode plates that are alternately superimposed one upon another with a separator interposed therebetween. In connection with this, as a method for inserting a separator between negative and positive electrode plates, there is known a technique whereby negative and positive electrode plates are alternately superimposed one upon another under a state where a pouch-shaped separator is attached to the positive or negative electrode plate.
An example of methods for attaching a pouch-shaped separator to an electrode plate will be described below. Firstly, as shown in FIG. 6A, a sheet-like separator 2 is so arranged as to cover both surfaces of an electrode plate 1. Subsequently, as shown in FIG. 6B, an ultrasonic bonding tool 31 is applied to a to-be-bonded edge of the separator 2. The ultrasonic bonding tool 31 has a width which is so set as to correspond to a width of a bonded portion 3. Thereby, the separator 2 receives, while being pressurized, ultrasonic vibration in a direction of a sheet surface thereof so as to be ultrasonically bonded. Lastly, as shown in FIG. 6C, a cutter 32 is applied to the central part of the bonded portion 3 to cut off the separator 2. In this way, the electrode plates 1 to which the pouch-shaped separator 2 is attached are consecutively produced.
In the conventional separator attaching method, the separator 2 made of a synthetic resin fiber cloth is subjected to ultrasonic bonding. However, in order for a fibrous material to be melted down by frictional heat resulting from ultrasonic vibration, application of ultrasonic vibration of large amplitude is required. This leads not only to an undesirable increase in running cost but also to the following problems. During bonding process, ultrasonic vibration is transmitted to the electrode plate 1. This causes active substances to fall off from the electrode plate 1, resulting in occurrence of minute short circuiting. Furthermore, whenever the cutter 32 is used to cut the bonded portion 3, a resin component contained in the separator 2 adheres to the blade of the cutter 32. This degrades the cutting capability of the cutter 32 in a short period of time and thus shortens its service life. Consequently, the amount of indirect materials tends to increase, and frequent halts of operations for cutter replacement are inevitable. This is undesirable from a cost standpoint.
The present invention has been made in light of the above stated problems with the conventional art, and accordingly it is an object of the present invention to provide a method and apparatus for attaching a separator to an electrode plate, the method and apparatus being free from a fear of minute short circuiting caused by the falling off of active substances from an electrode plate during the time a separator is shaped like a pouch by bonding, the method and apparatus being capable of cutting a bonded portion stably for a longer period of time without tool replacement, and requiring lower cost.
To achieve the above object, according to one aspect of the present invention, a method for attaching a separator to an electrode plate includes: a separator arrangement step for arranging a sheet-like separator so as to cover both surfaces of an electrode plate; a separator bonding step for thermally welding the separator by applying a first heating plate along a to-be-bonded edge of the separator adjacent to the electrode plate, the first heating plate having a width which is so set as to correspond to a width of a bonded portion of the separator; and a cutting step for cutting off the separator by pressing a second heating plate against substantially a central part of the bonded portion. In this method, since bonding of the separator is performed by thermal welding, no vibration occurs. This prevents active substances from falling off from the electrode plate, and thus prevents the possibility of minute short circuiting. Moreover, the separator is cut off by subliming its resin component through local heat transfer with use of a heating plate. Thus, cutting of the bonded portion is stably performed for a longer period of time without tool replacement, resulting in cost reduction.
According to another aspect of the invention, an apparatus for attaching a separator to an electrode plate, the apparatus that bonds a to-be-bonded edge, adjoining an electrode plate, of a separator which is so arranged as to cover both surfaces of the electrode plate and that cuts a central part of a bonded portion of the separator, includes: a bonding and cutting member composed of a heating plate with a width which is so set as to correspond to a width of the bonded portion, and having a cutting protrusion formed in one part thereof facing substantially the central part of the bonded portion. With this construction, bonding is performed without causing minute short circuiting, and further cutting of the bonded portion is stably performed for a longer period of time without tool replacement, which results in cost reduction. In addition, bonding and cutting are performed in combination in one process. This helps reduce the number of assembly man-hours, so that the cost is reduced greatly.
According to still another aspect of the invention, an apparatus for attaching a separator to an electrode plate, the apparatus that bonds a to-be-bonded edge, adjoining an electrode plate, of a separator which is so arranged as to cover both surfaces of the electrode plate and that cuts a central part of a bonded portion of the separator, includes: a heating plate for bonding having a width which is so set as to correspond to a width of the bonded portion; and a heating plate for cutting that cuts substantially the central part of the bonded portion.
While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings.